Autocomplete does not appear when trying to edit literals.  This is not
desirable behavior because when a user enters a URI into that box, it will not
be parsed as a URI, but rather entered as a literal into the document.

Example:

1. load http://dig.csail.mit.edu/2007/wiki/jambobo.rdf .
2. attempt to change the "creator" to "James Hollenbach" (no autocomplete appears)
3. assume James Hollenbach isn't in our database, so type
http://web.mit.edu/jambo/www/foaf.rdf#jambo
4. the URI is entered into the file as a literal, and therefore is not expandable.

The desirable behavior is definitely to put in actual links as much as possible,
because without the links our data won't be interesting at all.